Cushion for railroad ties comprising a copolymer of styrene and isobutylene, a bituminous material, and a fibrous material



Aug. 31, 1954 2,688,005 COMPRISING A COPOLYMER 32 6 :1 r v 83- Ul ll l 6 33 ETAL Filed April 30. 1952 R. E. CLAYTON, JR. CUSHION FOR RAILROAD TIES MATERIAL AND A FIBROUS MATERIAL OF STYRENE AND ISOBUTYLENE, A BITUMINOUS com? 008 oomT Thicknfiss, Inches m m mm a a e f V O Q m 5 a M t 58 n L.% Cru% m touc m mw PP Patented Aug. 31, 1954 CUSHION FOR RAILROAD TIES COMPRISING A COPOLYMER OF STYRENE AND ISOBU- TYLENE, A BITUMINOUS MATERIAL, AND A FIBROUS MATERIAL Robert E. Clayton, Jr., and Raymond G. Newberg, Roselle Park, N. J., assignors to Standard Oil Development Company, a corporation of Delaware Application April 30, 1952, Serial No. 285,251

2 Claims.

This invention relates to a means for inhibiting the breakdown of railroad ties and more particularly relates to a cushioning composition adapted to be placed between the rail and the tie.

Railroad ties break down because of the pounding they receive when the rails beat against the tie plates during the passage of the trains. The resultant destruction is so great that 40,000,000 ties must be replaced each year. Many attempts have been made in the past to protect the ties against such mechanical breakdowns. Generally, this has taken the form of placing a cushioning material between the tie and the tie plate. Rubber and rubbery materials are among the many types of materials tried. None of these materials have been found suitable. Unvulcanized rubber is unsuitable because it is squeezed out of the area which it is meant to protect. Vulcanized rubber was also found ineiiective for the same reason although to a lesser extent. Furthermore, it was found to be ground into dust to some extent. Polyethylene behaved similarly to unvulcanized rubber. Polystyrene was easily crushed into a powder.

It has now been found that a composition comprising bituminous material, a copolymer of styrene and isobutylene and a fibrous material has the unique property of flowing sufficiently as to take the contour of the tie, i. e., to seat itself properly, yet without flowing so much as to be squeezed excessively out of place.

The bituminous material to be used in the above composition may be selected from a wide variety of m ural and industrial products. For instance, various natural asphalts may be used, such as natural Trinidad, Bermudez, Gilsonite, grahamite and Cuban. Various petroleum asphalts may be used such as those obtained from California or Mid-Continent crudes. Mexican petroleum asphalt, as well as tarry residues known as cracking coil tar obtained as a byproduct during the cracking of gas oil or other heavier petroleum fractions to obtain gasoline or other lighter fractions. Although the above mentioned natural and petroleum asphalts are preferred, still further bituminous materials may be used such as coal tar, wood tar and pitches obtained from various industrial processes, such as fatty acid pitch.

The copolymer to be used in the composition of the present invention comprises a cycalkene copolymer having an intrinsic viscosity preferably greater than 1.00 and having a content of combined styrene or other cyclic constituents of 40 to preferably 50%, such copolymers being produced at copolymerization temperatures below 50 C., and preferably below -'70 C., a suitable operating temperature being -103 C. since this is the boiling point of liquefied ethylene. Copolymers having the desired high intrinsic viscosity cannot be produced at more elevated temperatures such as between 0 C. and 50 C.

The intrinsic viscosity may be determined in a suitable solvent such as toluene, using the following formula for calculating the intrinsic viscosity:

2.303l0g relative viscosity Intrmslc vlscosl'ty Concentration of copolymer/ ml Instead of isobutylene, other aliphatic monoolefins may be used, preferably having more than 2 carbon atoms and preferably iso-olefins having 4 to 8 carbon atoms, such as isopentene (methyl- Z-butene-l) or a pentene obtained by dehydra tion of secondary amyl alcohol.

Instead of styrene, other polymerizable, monooleiinic aromatic hydrocarbons may be used, such as indene, the homologues of styrene, e. g., alphamethyl styrene, paramethyl styrene, alphamethyl paramethyl styrene or dihydro naphthalene.

The copolymerization is effected by mixing the two reactants, with or without a mutual solvent. if necessary, such as ethylene, propane, butane, methyl chloride or refined naphtha, and then after the cooling of the reactants to the desired low temperature, adding a Friedel-Crafts halide catalyst such as boron fluoride or boron fluoride catalyst activated by the addition of 0.1% of diethyl ether, aluminum chloride, titanium tetrachloride, or aluminum alkoxide-aluminum chloride complex (AlCls.A1(OC2Hs)s). If desired, such catalyst may be dissolved in a solvent such as carbon disulfide, a low molecular weight sulfur-free saturated hydrocarbon, a lower allzyl halide, e. g., methyl chloride, or ethyl chloride or a mixture of methyl chloride with butane at or below the boiling point of the catalyst solvent, and then the catalyst solution cooled down, filtered and added to the reaction mixture. Alternative catalysts include:

BFs solution in ethylene, activated BFa catalyst in methyl chloride solution. Volatile solvents or diluents, e. g., propane, ethane, ethylene, methyl chloride, alkyl halides, methylene chloride or carbon dioxide (liquid or solid) may also serve as internal or external refrigerants to carry off the liberated heat of polymerization. After completion of the copolymerization, residual catalyst is hydrolysed with alcohol, for example, isopropyl and excess catalyst removed by washing the product with water and preferably also with dilute aqueous caustic soda. The resulting solid copolymer may range from a viscous fluid or a relatively stiff plastic mass to a hard, tough, thermoplastic resinous solid, depending upon the temperature of polymerization, the yield of polymer obtained upon the active feed, and the temperature at which the physical texture is observed.

When copolymers are prepared according to this invention, i. e. with a combined content of 40 to 60%,. using copolymerization temperatures below 50 C., the resultant copolymers will generally have average molecular weights above 6,000, and preferably 10,000 to 150,000, with intrinsic viscosities above 0.8 and preferably above 1.30. The higher molecular weight and intrinsic viscosities are obtained with the lowest copolymerization temperatures, and they are also favored by the lower content of cyclic reactant, i. e., a per cent of combined styrene of 40 to 60%. The hardness of the copolymer generally increases with increasing content of combined styrene or other cyclic constituents.

Thus the preferred operating conditions for making the copolymers for use according to this invention comprise copolymerizing a reaction mixture containing 40 to 60% of styrene and balance isobutylene, at a temperature below -70 C. in the presence of about 1-4 volumes of methyl chloride or other lower alkyl halides per volume of active polymerization feed, and using as the catalyst the solution of aluminum chloride dissolved in methyl chloride or other lower alkyl halides.

The fibrous material to be used in the composition of this invention may be any suitable fibrous material such as nylon, Orlon, Dacron, dynel, glass, cotton, wool, leather, wood, rayon, silk and asbestos. Of these fibers, asbestos is by far the best since it is cheap, chemically inert,

tough, and pressure resistant. The fibers may vary in length as desired. For example, when using asbestos, it may vary from group 4 to group 7 (Canadian Asbestos Classification), i. e., from shingle fiber to shorts. The other fibers may vary accordingly.

The concentration of each of the ingredients may vary. The polymer and asphalt concentration may each vary from to 35% of the total mixture; the fiber concentration may vary from 30 to 70%, all being percent by wt.

The advantages of the invention will be better understood from a consideration of the following experimental data which are given for the sake of illustration, but without intention of limiting the invention thereto.

A composition consisting of of a copolymer of 50% isobutylene and 50% styrene, 25%

of petroleum asphalt having a softening point of 220 F. and of a short fiber asbestos known as chrysolite was prepared and tested in a parallel plate plastometer enclosed in a circulating oven at 120 F. Cylindrical test specimens &2 inch in diameter were conditioned for two hours in the oven at 120 F. before being placed in the plastometer. The compressive force exerted on the specimen was 100 kilograms or 800 pounds per square inch. The temperature and pressure used are the maximum that should be encountered in actual railroad service.

The curves in the accompanying graph show the fiow properties of the composition of this invention in terms of diminishing thickness as a function of time. When the load was applied, the-specimen initially exhibited appreciable flow. The rate of flow then diminished until after one day it had ceased. However, when the specimen was removed, it was found to have increased in diameter; which meant that during test the load per unit area had decreased. In order to bring the load back to the maximum desired, the specimen was recut to the original inch diameter, reconditioned for two hours at 120 F. and placed back in the plastometer. Data were then obtained as plotted in the curve captioned 2nd Cut. This curve showed that the flow under 800 pounds per square inch had not been completed as indicated by the initial curve. Also, the specimen diameter increased anew. The recutting and retesting were then repeated again, and the 3rd Cut curve was obtained. This time little flow was exhibited throughout the entire time of test. However, a thin trimming was still possible; so the recutting and retesting were repeated once more and the data were plotted in the curve captioned 4th Cut.

In other words, when the composition is first compressed, it will flow. But there is a practical limit to the amount of flow. It will seat itself properly, but will not all be squashed away. The final thickness that can be depended upon is ample.

The nature of the present invention having been thus fully set forth and specific examples of the same given, what is claimed as new and useful and desired to be secured by Letters Patent 1. A cushioning composition for railroad ties consisting of 15 to 35% by weight of a copolymer of to 40% by weight isobutylene and 40 to 60% by weight of styrene, 15 to 35% by weight of petroleum asphalt, and 30 to by weight of asbestos.

2. A cushioning composition for railroad ties consisting of 25% by weight of a copolymer of 50% by weight of isobutylene and 50% by weight of styrene, 25% by weight of petroleum asphalt having a softening point of 220 F. and 50% of short fiber asbestos.

References Cited in the file of this patent FOREIGN PATENTS Number 

1. A CUSHIONING COMPOSITION FOR RAILROAD TIES CONSISTING OF 15 TO 35% BY WEIGHT OF A COPOLYMER OF 60 TO 40% BY WEIGHT ISOBUTYLENE AND 40 TO 60% BY WEIGHT OF STYRENE, 15 TO 35% BY WEIGHT OF PETROLEUM ASPHALT, AND 30 TO 70% BY WEIGHT OF ASBESTOS. 